Pressure responsive switch with improved diaphragm operating means

ABSTRACT

A differential pressure-sensitive microelectric switch of low profile made possible by placing both high and low pressure connections on the same side of a flexible diaphragm and utilizing a range spring mounted to undergo tension and contraction in a direction perpendicular to the motion of the diaphragm. The spring is connected to the short arm of a bellcrank lever, the longer arm of which is engaged by the diaphragm and in turn operates the switch. Because of the leverage, the spring travel is small as compared to diaphragm and switch operating arm travel. By providing annular grooves in the housing members on each side of the diaphragm, aligned with passageways through the rim of the diaphragm and by providing a passageway from the high pressure connection to the groove on the same side of the diaphragm as the connection, the unit can be assembled without the necessity of lining up the parts of the device.

United States Patent 72] Inventors James W. Phillips;

Richard S. Zoludow, South Bend, Ind. [21] Appl. No. 735,339 [22] FiledJune 7, 1968 [45] Patented Feb. 23, 1971 [73] Assignee F. W. Dwyer Mfg.Co., Inc.

[54] PRESSURE RESPONSIVE SWITCH WITH IMPROVED DIAPHRAGM OPERATING MEANS9 Claims, 14 Drawing Figs.

[52] U.S. Cl 200/83, 200/153 [51] Int. Cl H01h 35/40 [50] Field ofSearch ZOO/81.9, 83 (all); 92/99, 100; 200/153. 19; 73/407 [56]References Cited UNITED STATES PATENTS 2,651,316 9/1953 Fageol 92/1002,719,889 10/1955 Miller ...200/153(.19)X 2,936,785 5/1967 Hastings92/99X 2,952,753 9/1960 Kmiecik et al ZOO/81.9 3,345,480 10/1967 Zeller200/83 2,722,837 11/1955 Dwyer 73/407 Primary Examiner- Robert S. MaconAssistant Examiner.l. R. Scott Attorney-Mann, Brown, Bradley ABSTRACT: Adifferential pressure-sensitive microelectric switch of low profile madepossible by placing both high and low pressure connections on the sameside of a flexible diaphragm and utilizing a range spring mounted toundergo tension and contraction in a direction perpendicular to themotion of the diaphragm. The spring is connected to the short arm of abellcrank lever, the longer arm of which is engaged by the diaphragm andin turn operates the switch. Because of the leverage, the spring travelis small as compared to diaphragm and switch operating arm travel. Byproviding annular grooves in the housing members on each side of thediaphragm, aligned with passageways through the rim of the diaphragm andby providing a passageway from the high pressure connection to thegroove on the same side of the diaphragm as the connection, the unit canbe assembled without the necessity of lining up the parts of the device.

BRIEF SUMMARY OF THE INVENTION Conventional pressure-sensitivemicroelectrical switches customarily are fabricated with the highpressure and low pressure connections on opposite sides of the diaphragmand with the range spring mounted between the diaphragm and switch sothat the spring expands and contracts in the same direction of movementas the diaphragm. This construction necessitates a high profile and alsointroduces an element of inaccuracy because of the change in spring ratewith change in elongation of the spring.

The differential pressure-sensitive switch of this invention has a lowprofile due to the novel construction features involving placing thehigh and low pressure connections on the same side of the diaphragm andmounting the spring so that it expauds and contracts in a direction.perpendicular to the direction of movement of the diaphragm. This ismade possible by using a bellcrank lever having a short and long armwith the spring attached to the short arm and the long arm being engagedby the diaphragm and in turn operating the switch. A mechanicaladvantage is realized by virtue of which the range spring expands andcontracts over a shorter distance than the travel of the switchoperating arm.

By the novel construction of the diaphragm and diaphragm housing inwhich the housing on each side of the diaphragm is formed with anannular groove communicating with each other through passageways in therim of the diaphragm, the

fluid pressure from the high pressure connection is able to pass fromone side of the diaphragm to the other without the necessity of havingto line up the parts during assembly.

It is an object of the invention to provide a low profile differentialpressure-sensitive switch. It is another object of the invention toprovide a switch which can be assembled without the necessity ofaligning the components. It is a further object of the invention toprovide a snap switch in which an element is interposed between thediaphragm and the switch to amplify the movement of the diaphragm. Astill further object of the invention is to provide a construction in adifferential pressure switch which permits the use of either a tensionor compression spring thereby enabling different characteristics to beachieved. Still another object of the invention is to provide adifferential pressure-sensitive switch having adjusting means exteriorlyavailable to change either the tension or compression of the spring.Another object of the invention is to provide a pressure-sensitiveswitch having visible means for determining the set point for the switchand for observing the on and off positions of the switch. Other objectsof the invention will become apparent from the following detaileddescription.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an elevational view of aswitch in accordance with the invention;

FIG. 2 is a top plan view of a pressure switch in accordance with theinvention with the conduit enclosure removed;

FIG. 3 is an elevational view of a switch in accordance with theinvention rotated through 90 from FIG. I and with the conduit enclosureremoved;

FIG. 4 is a cross-sectional view of the pressure switch taken along line4-4 of FIG. 2;

FIG. 5 is a cross section taken along the line 5-5 of FIG. 2;

FIG. 6 is a bottom plan view of the base of the pressure switch;

FIG. 7 is a vertical cross section of the base of the novel pressureswitch taken along line 77 of FIG. 6;

FIG. 8 is a cross section of the base fon'ning part of the switchstructure taken along the line 8-8 of FIG. 6;

FIG. S9 is a plan view looking at the inner surface of the housingforming part of the pressure switch;

FIG. 10 is a vertical cross section through the center of the diaphragmforming part of the pressure switch;

FIG. 11 is a plan view of the high pressure side of the diaphragm;

FIG. I2 is a plan view of the input lever forming part of the switch;

FIG. 13 is a front elevational view of the input lever; and FIG. 14 is aside elevational view of the input lever.

DETAILED DESCRIPTION Referring to the drawings particularly FIGS. 3, 4,5 and 7 the numeral 1 indicates the pressure switch base which may bedie cast from zinc or other suitable metal or the base may be moldedfrom suitable plastic material, preferably one that is transparent. Thebase 1 is formed with low pressure inlet or connection 3 and highpressure inlet or connection 5 and with an elongated recessed portion 7in which is mounted the range spring 9 and range spring adjusting screw11 (FIG. 4). High pressure connection 5 is connected to a diagonalpassageway 13, the other end of which opens into an annular groove 15formed in the surface 17 adapted to seat against the rim 18 of thediaphragm 19 (FIG. 10). The base 1 is also formed with an elongatedopening 21 in which is mounted an electric microswitch 23. As shown inFIG. 2 microswitch 23 has three terminals in order to enable the switchto be connected so that it is normally in open position or normally inclosed position. Housing 25 is fastened to the base 1 by bending the endportion 27 over the flange 29 of the base 1. Housing 25 may be stampedout of cold rolled steel or may be molded from suitable plasticmaterial.

Mounted in housing 25 is a flexible diaphragm 19 formed with smallspaced passageways 31 in the rim portion of the diaphragm communicatingthe surfaces with each other. As shown in FIG. 11 there are three suchpassageways 3] equally spaced around the rim portion of the diaphragmalthough this number may be greater or less. The diaphragm 19 ispreferably made of neoprene but can be made of any other elastomer whichhas the desired flexibility and resistance to the chemical action of thefluid housing pressure to which it is to be regulated and which has therequisite mechanical properties. As shown in FIGS. 10 and 11, thediaphragm is formed with an annular rib 33 at the periphery of thediaphragm and with a series of radial ribs 35 to impart additionalmechanical strength thereto. On the opposite surface are two upstandingprojections 37 to hold diaphragm plate 39 (FIG. 5) secure to the uppersurface of the diaphragm. The diaphragm plate 39 is formed with twoholes coincident with the projections 37, the holes being slightlysmaller in cross-sectional area than the heads of the projections 37 sothat the plate can be pressed down against the diaphragm with the headsof the projections 37 extending through the plate and holding it firmlyagainst the face of the diaphragm. Interiorly of the rim portion of thediaphragm the diaphragm is formed with a thin convoluted annular portion41 to allow the diaphragm to move easily with small changes in pressure.

Referring to FIGS. 5, 7 and 8 it will be seen that the rim portion 17 ofthe base 1 has an annular groove 15 into which the passageway 13 extendsfrom the high pressure connection 5. As shown more clearly in FIG. 5,the annular groove 15 is directly in line with the passageways 31 of thediaphragm when the switch is assembled.

Referring more particularly to FIGS. 5 and 9, it will be seen that thehousing 25 has an annular recess 43 adjacent the wall 45. Inwardly ofthe recess the housing is formed with two closely spaced upstandingannular walls 47 on which the rim of the diaphragm is adapted to seat.Four equally spaced radial grooves 49 connect the recess 43 with thehigh pressure space between the central portion of the diaphragm andhousing 25. The housing is formed with the four spaced semisphericalprotuberances 51 to prevent the diaphragm from snugly contacting theinner face of housing 25.

The base 1 is formed with the downwardly projecting annular flange 53and flat surfaces 17 and 20. Surfaces l7 and 20 together with theupstanding walls 47 of the housing form a fluidtight seal with thediaphragm. The outer diameter of flange 53 is slightly less than thediameter of inner wall 47 and serves as a locator. It will be evidentthat the fluid pressure from fluid entering the low pressure connection3 and then passing through port 55 is impressed only on the low pressureside of the diaphragm by virtue of the leakproof seal formed by the flatsurfaces 17 and 20 and upstanding walls 47 with the rim of thediaphragm. It will also be apparent that since the diagonal passageway13 through the base 1 connects with groove 15 which is outside of theflat surface 20, the high pressure fluid cannot enter the low pressureside of the diaphragm but can pass only from groove 15'through thepassageways 31 in the diaphragm into the recess 43 of the housing andthence through radial recesses 49 into the space on the opposite or highpressure side of the diaphragm.

Referring more particularly to FIGS. 4, and 7. mounted in the recess 7of the housing 1 is adjusting screw 11 and range spring 9. The adjustingscrew may be made of steel, brass, nylon or another suitable material.The screw 11 is formed with an exteriorly exposed adjusting head 57having a kerf in order to enable it to be rotated by a screw driver inan opening formed in the end wall 59 of recess 7. The head 57 is sealedby an O-ring to prevent leakage. Adjusting nut 61 is screwably mountedon screw 11. The head of adjusting nut 61 is adapted to ride in recess 7and is shaped to that it will not turn. As shown, the recess 7 has arectangular cross section. The head of the adjusting nut 61 is thereforepreferably of rectangular cross section but slightly smaller than incross-sectional area than the recess 7 so that it can move back andforth with binding against the walls of the recess.

Range spring 9 is a coil spring fastened at one end to adjusting nut 61.One method of fastening is to provide the adjusting nut 61 with helicalgrooves 63 onto which one end of the spring is turned. The other end oftherange spring 9 is fastened to input lever 65 (FIG. 4).

As shown in FIGS. 12, 13 and 14, input lever 65 is made in the form of abellcrank with a short arm 67 and a long arm 69. The input lever 65 ispreferably made lightweight so as to offer the least resistance possibleto movement. The input lever is preferably stamped out of thin sheetmetal with two eyelets 71 formed integrally with the bellcrank andextending rearward from the short arm 67 to act as a pivot or fulcrum.The short arm 67 is formed with openings 73 and 75 with a band of metal77 therebetween to which the other curved end of the range spring isattached by inserting one end through opening 73 around the back of band77 and thence through opening 75. As shown in FIG. 12, the long arm 69has one edge 79 cut on the bias to remove unnecessary metal. The otheredge 81 lies directly under the microswitch and has three contact knobs83 which may be welded onto the long arm or they may be small screwsinserted in spaced openings in the arm. By

providing more then one contact point, the differential of the devicecan be increased or decreased by virtue of the different positions ofthe diaphragm at which the long arm contacts the mieroswitch actuatinglever 84. The long arm of the input lever has a center portion 85removed to reduce weight. The walls 87 of the center portion are bent atright angles to the plate in order to impart rigidity thereto. Similarlythe long sides 88 of the long arm are bent in the opposite direction toimpart rigidity. Portions of the short arm 67 are also bent out of theplane of the arm as shown at 89 and 91, preferably at right anglesthereto, in order to impart additional rigidity. A rib 92 also acts as areinforcing member to retain the two arms at anlangle of 90 to eachother.

input lever 65 is mounted on the inside of the base by means of a rod 93passing through eyelets 71 and seated in grooves 95 (FIGS. 6 and 8).Threaded holes 97 are tapped in the base adjacent to the rounded grooves95 through which screws 96 can be threaded, the heads of which bearagainst the shaft 93 and hold it securely in place. It will be seen fromFIGS. 4 and 5 that the long arm 69 of the input lever 65 is always incontact with the spherical protuberance 99 in the center of thediaphragm plate.

In the event that it is desired to provide an adjusting screw which iscalibrated and can be visually seen, base 1 may be made of a transparentplastic material or the recess 7 may have a separate top wall which istransparent and which may be fastened to the base in any suitable way asby means of screws. As shown in P10. 2, where the top wall of the recessis transparent it will have calibration marks thereof shown as numbers 1to 6 inclusive so that the tension on the range spring can be determinedby the position of the adjusting nut 61. There may also be a visibleswitch position indicator 100 to indicate when the switch is on or off.

The device of this invention preferably has a conduit enclosure 101which is preferably a rectangular shaped enclosure formed of cold rolledsteel or other suitable material having four laterally extending tabs103, integral with enclosure 101 and adapted to fit on studs 105 eastintegrally with the base. The enclosure 101 has an opening 107 throughwhich the electrical conduits can be attached to the terminals of themicroswitch. A removable lid 109 is fastened to the enclosure by meansof screw 111. A suitable bracket 113 may be mounted on two of the studs105 for mounting the guage on a wall or other suitable place. Theenclosure 101 and the bracket 113 are held on the studs by means ofsuitable nuts 1 15.

The operation of the device should be apparent from the followingdescription. By turning the screw head 57, the adjusting nut 61 is setto open or close the switch at the desired pressure differential andthereby control the operation of a compressor, evacuating pump or othersystem involving differential pressure. Due to the fact that the devicecan be used with a normally open or normally closed switch and due tothe fact that the range spring can either be a spring which is nor mallyunder compression or normally under tension, the switch has universalapplication.

We claim:

1. in a low profile differential pressure sensitive electric switchwherein a flexible diaphragm is mounted in a housing with means forapplying low pressure on one side and high pressure on the other side ofthe diaphragm and means activated by the diaphragm for opening andclosing an electric switch, the improvement wherein said activatingmeans comprises:

a bellcrank pivotally mounted in said housing, one arm of said crankbeing substantially longer than the other arm thereof and extending in adirection generally parallel to said diaphragm;

calibrated range spring means positioned in said housing;

said spring means comprising a coil spring, the axis of which isperpendicular to the axis of movement of the diaphragm;

one end of said spring engaging the shorter arm of said crank and theother end of said spring being engaged by means for adjusting thetension or compression of said spring; with the longer arm of said crankbeing in operative engagement with the diaphragm and the switch.

2. A differential pressure sensitive electric switch in accordance withclaim 1 in which:

said adjusting means comprises a threaded element rotatably mounted inand operable from the exterior of said housing;

a nut threadedly received on said element;

said nut being mounted for movement longitudinally of said element;

means for restraining said nut against rotational movement on rotationof said element;

and means for securing said other end of said spring to said nut;

the axis of said element being substantially coincident with that of thespring.

3. A differential pressure sensitive switch in accordance with claim 1in which:

said housing being provided with low and high pressure connections onthe same side of said diaphragm;

said diaphragm having at least one passageway through the rim thereof;

one of said connections communicating with the passageway through thediaphragm rim;

means being provided for clamping said diaphragm rim in fluidtightrelationship between the top and bottom of said housing; and

means being provided for communicating the space on the side of thediaphragm opposite the side on which said inlet and outlet are placed,with said passageway in said rim.

4. A difierential pressure sensitive switch in accordance with claim 3in which:

said means for communicating said passageway through the rim of saiddiaphragm with oneof said connections includes an annular groove in thesurface of the top and bottom housing members between which the rim ofthe diaphragm is clamped;

said passageway communicating between said grooves.

5 A differential pressure sensitive switch in accordance with claim 4 inwhich: the annular groove in the housing member on which saidconnections are not mounted, is connected by at least one radiallydirected passageway to the space between the diaphragm and said member.

6. A differential pressure sensitive switch in accordance with claim 5in which: the rim of the diaphragm is clamped in fluidtight relationshipbetween the top and bottom housing members inwardly of the locationofsaid passageway in the diaphragm rim.

7. A differential pressure sensitive switch in accordance with claim 6in which:

there are a plurality of spaced passageways in the rim of saiddiaphragm; and

a plurality of spaced radially directed passageways connecting theannular groove to the space between the diaphragm and housing member.

8. A differential pressure sensitive switch in accordance with claim 3in which:

said spring means is a coil spring the axisof which is perpendicular tothe axis of the diaphragm; and

the other end of said spring is engaged by means for adjusting thetension or compression of said spring.

9. A ditferential pressure sensitive switch in accordance with claim 8in which: said adjusting means is a threaded element operable from theexterior of said housing, the axis of said element being substantiallycoincident with that of the spring, said threaded element being movableaxially in opposite directions.

m UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.25554160 Dated February 23, 1971 Inven James W; Phillips et a1 It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

F- On identification page for Attorney read MANN, BROWN,

McWILLIAMS 8c BRADWA Column 5, line 21, after begin a new paragraph.Column 6, line, 1, after begin a new paragraph. Column 6, lime 19, afterbegin a new paragraph.

Signed, and sealed this 13th day of July 1971 (SEAL) "Atte st:

EDWARD mms'rcnsmm. WILLIAM E. SCHUYLER Attesting Officer Commissioner ofPat

1. In a low profile differential pressure sensitive electric switchwherein a flexible diaphragm is mountEd in a housing with means forapplying low pressure on one side and high pressure on the other side ofthe diaphragm and means activated by the diaphragm for opening andclosing an electric switch, the improvement wherein said activatingmeans comprises: a bellcrank pivotally mounted in said housing, one armof said crank being substantially longer than the other arm thereof andextending in a direction generally parallel to said diaphragm;calibrated range spring means positioned in said housing; said springmeans comprising a coil spring, the axis of which is perpendicular tothe axis of movement of the diaphragm; one end of said spring engagingthe shorter arm of said crank and the other end of said spring beingengaged by means for adjusting the tension or compression of saidspring; with the longer arm of said crank being in operative engagementwith the diaphragm and the switch.
 2. A differential pressure sensitiveelectric switch in accordance with claim 1 in which: said adjustingmeans comprises a threaded element rotatably mounted in and operablefrom the exterior of said housing; a nut threadedly received on saidelement; said nut being mounted for movement longitudinally of saidelement; means for restraining said nut against rotational movement onrotation of said element; and means for securing said other end of saidspring to said nut; the axis of said element being substantiallycoincident with that of the spring.
 3. A differential pressure sensitiveswitch in accordance with claim 1 in which: said housing being providedwith low and high pressure connections on the same side of saiddiaphragm; said diaphragm having at least one passageway through the rimthereof; one of said connections communicating with the passagewaythrough the diaphragm rim; means being provided for clamping saiddiaphragm rim in fluidtight relationship between the top and bottom ofsaid housing; and means being provided for communicating the space onthe side of the diaphragm opposite the side on which said inlet andoutlet are placed, with said passageway in said rim.
 4. A differentialpressure sensitive switch in accordance with claim 3 in which: saidmeans for communicating said passageway through the rim of saiddiaphragm with one of said connections includes an annular groove in thesurface of the top and bottom housing members between which the rim ofthe diaphragm is clamped; said passageway communicating between saidgrooves. 5 A differential pressure sensitive switch in accordance withclaim 4 in which: the annular groove in the housing member on which saidconnections are not mounted, is connected by at least one radiallydirected passageway to the space between the diaphragm and said member.6. A differential pressure sensitive switch in accordance with claim 5in which: the rim of the diaphragm is clamped in fluidtight relationshipbetween the top and bottom housing members inwardly of the location ofsaid passageway in the diaphragm rim.
 7. A differential pressuresensitive switch in accordance with claim 6 in which: there are aplurality of spaced passageways in the rim of said diaphragm; and aplurality of spaced radially directed passageways connecting the annulargroove to the space between the diaphragm and housing member.
 8. Adifferential pressure sensitive switch in accordance with claim 3 inwhich: said spring means is a coil spring the axis of which isperpendicular to the axis of the diaphragm; and the other end of saidspring is engaged by means for adjusting the tension or compression ofsaid spring.
 9. A differential pressure sensitive switch in accordancewith claim 8 in which: said adjusting means is a threaded elementoperable from the exterior of said housing, the axis of said elementbeing substantially coincident with that of the spring, said threadedelement being movable axially in opposite directions.